For fixed \(L\) , Problem (REF ) is a convex problem and therefore can be directly solved [1]}. The result is given by Theorem REF .
 [t]
Proposed Aerial-RIS Setup Algorithm
[1]
Source power minimization
Find \(\mathbf {q}_m^* = \xi _m\mathbf {w}_m\)  by (REF ) and determine \(\mathbf {q}^*\)  by (REF )
Determine \(\mathbf {\bar{\rho }}^*\)  by (REF )
Compare \(\frac{\Delta \phi _{\mathrm {HPBW}}}{2}\)  and \(\Delta \phi _{\max }\triangleq \max _{m\in \mathbb {M}} |\Delta \phi _m(\bar{\rho }^*)|\) 
\(\frac{\Delta \phi _{\mathrm {HPBW}}}{2} > \Delta \phi _{\max }\) 
Apply full-array structure \(\left(\bar{N}=N\right)\) 
Find the RIS phase \(\left\lbrace \theta _n^*\left(\mathbf {q}^*,\mathbf {\bar{\rho }}^*\right)\right\rbrace _{n=1}^N\)  by (REF )
 (sub-array structure \(\left(\bar{N}<N\right)\) )
\(L=2\)  to \(L_{\max }\) 
[t]@X@
Divide \(\mathbb {M}\)  into \(\left\lbrace \mathbb {M}_i\right\rbrace _{i=1}^L\)  based on (REF )


Divide the RIS array into \(L\)  sub-arrays by (REF )
[t]@X@
Determine
